Recently, due to unique physical and structural characteristics of a low dimensional semiconductor nanostructure, a study for using the low dimensional semiconductor nanostructure as a high-performance element using a semiconductor nanowire has been actively conducted. As compared with single crystal semiconductors formed of a single element such as silicon (Si), germanium (Ge), or the like, compound semiconductors formed of two kinds or more elements may implement several kinds of semiconductor nanoelements appropriate for purposes using a combination and a composition ratio of various elements.
Among them, a gallium arsenide, which is a group III-V semiconductor, may fabricate many high-speed integrated circuits due to a moving speed of electrons five times faster than that of silicon and a simple transistor structure. In addition, the gallium arsenide may process a high frequency band up to 250 GHz, and is less affected by a temperature change, such that noise at the time of an operation is lower than that of the silicon. First of all, the gallium arsenide has direct bandgap semiconductor characteristics to have excellent light emitting efficiency. Therefore, recently, the gallium arsenide has become prominent as a material of a light emitting diode (LED) or a solar cell module that has been rapidly grown.
Therefore, in order to use gallium arsenide nanowires as an actual element, it should be first performed to spatially align well a high-quality vertically-aligned gallium arsenide semiconductor nanowire array having a wide surface area and a large aspect ratio and adjust a density of the high-quality vertically-aligned gallium arsenide semiconductor nanowire array as well as it is necessary to uniformly control diameters and lengths of the nanowires.
According to reports up to now, a method for growing the gallium arsenide nanowires may be mainly classified into a top-down method and a bottom-up method.
The gallium arsenide nanowires may be grown using molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), or the like, as the top-down method. However, in the top-down method, a defect such as a twin occurs at the time of growing the nanowires, and it is difficult to vertically align the nanowires having a uniform length and diameter from a substrate. In addition, the bottom-up method may be divided into dry etching and wet etching. Reactive ion etching (ME), which is a representative example of the dry etching, requires expensive equipment, may cause damage to a material in a process, and may cause a surface that is non-uniform and includes a large amount of impurities. Therefore, the RIE may have a large influence on physical and chemical characteristics, such that it may become a variable in designing an element, which is not preferable.
Meanwhile, the wet etching of which a representative example is metal-assisted chemical etching has been most actively studied currently in fabricating silicon nanowires, and is a method for obtaining nanowires of which lengths and diameters are controlled at a short time by immersing a patterned thin film in an etchant including an oxidizing agent using a metal as a catalyst to induce a spontaneous reaction. A study range of this method has increased in fabricating group III-V semiconductor nanowires including the gallium arsenide.
However, in the case of a group III-V semiconductor substrate including the gallium arsenide, at the time of performing chemical etching using the metal as the catalyst, vertical etching and side etching are simultaneously generated, such that it is difficult to fabricate nanowires having a uniform diameter and length and it is difficult to fabricate nanowires having a large aspect ratio.